If your choices are only the the two mentioned, these area few things to consider.
The Kreighoff..
Nicely made rifle good overall quality.
Decocking safety both good and bad.
Overall fit and finish good.
Shape and appearance to each their own but I like it.
On the minus side.
Decocking safety is very safe, however it's also very stiff to operate if needed in a big hurry and especially with sweaty or bloody hands it could be a problem.
The decocking safety does not allow for ejectors. That is a deal killer for me no ejectors no rifle in my opinon. I won't own one. My experiences are that when one needs ejectors he needs them very badly.
The Krieghoff has a reputation of doubling after some use.
The Merkel,
A handsome rifle for the price.
It is available with ejectors.
Overall fit and finish is average.
I find them to look a bit cheesy especially the ones that come with that cartoon character engraving.
They are very front end heavy IMO and stiff to operate.
They are built on the same action as their shotguns whether this is good or bad I don't kow but it's something to consider.
I have been told that they tend to be pretty reliable.
Neither of these rifles are custom fit to you the shooter and are mass produced. I would rather have a custom fit rifle.
For the money there is no better working double than a Searcy. A chapuis is right up there as well.
This is my humble opinon only, it ultimatley boils down to what you want the rifle for and what you like and expect from your firearm.
Nico,
Yes that is my article...
Couldn't you tell from the ugly dude behind the buff..